"baffless" sump?

I had to do the same thing. I pulled the rock and left the sand in. Just a bit of water barely covering the sand. I could not believe how heavy it was!!! Good thing I had a buddy close by, no way I would let my wife even try to help with that move.
 
I pretty much gave up on the idea. I moved some of the rubble into the main tank and put the old sump back in.

I'm returning the 20L today, and ordering another hydor koralia powerhead. I just got one the other day, and I love it! Works way better than the standard style powerheads, and looks cleaner, too
 
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